Developmental delay and intellectual disability

Chromosome microarray (CMA) is now considered a first-line genetic test for the investigation of DD, ID, autism spectrum disorder (ASD), and congenital abnormalities.² CMA does not detect gene variants causing FXS (ie FMR1 gene), so an additional deoxyribonucleic acid (DNA) test must be ordered alongside.

While general practitioners (GPs) are able to order CMAs, many choose not to, given the complex interpretation of the results. However, ordering CMA and FXS tests in parallel with referral to a paediatrician can reduce waiting times for patients.

A Medicare Benefits Schedule (MBS) rebate is available for CMA in situations where the patient has DD, ID, ASD or at least two congenital abnormalities. DNA testing for FXS is available with an MBS rebate when the patient:³

• exhibits ID, ataxia, neurodegeneration, or premature ovarian failure consistent with an FMR1 mutation
• has a relative with an FMR1 mutation.

A genetic cause should be suspected in individuals with DD and any of the following:

• dysmorphic features
• autistic features
• epilepsy
• congenital anomalies (eg cleft palate, heart defects)
• a family history of autism, FXS or other developmental/learning disability.

Patients with these features should be referred to a paediatrician or genetics services.

Refer directly to a paediatric neurologist if there is regression of motor skills (eg suspected muscular dystrophy, spinal muscular atrophy).

Raising Children Network, Developmental delay in babies